How to retrieve XYZ co-ordinates from a raw depth image?

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In the first link what would I have to subscribe to in order to get the const cv::Mat& intr_rect_ir? Is that the rectified ir image?

If you see closely, in the next few lines of code, cx,cy,fx and fy are calculated from intr_rect_ir. It basically is matrix representation of camera parameters. if you know the camera parameters, you can either directly give them or subscribe to the camera_info topic from Kinect and copy the parameters into a OpencvMat. It would be recommended to use calibrated parameters of "IR depth camera" of Kinect or else all the Kinects have same IR camera matrix.

In another part of my code I am using the rgb camera stream and can therefore not subscribe to both the rgb and ir stream. Would it still give me the same point cloud if I use the rgb camera info?

no, you cannot use like that. The RGB camera parameters are different from the depth camera parameters and both are always constant. So instead of subscribing to the camera parameters, you can simply hard code into the program.

When I checked the ir camera info it is exactly the same as the rgb info. Is this possible?

may be you are seeing something wrong. Just to say that the camera parameters will be different , have a look at this link http://vision.in.tum.de/data/datasets...

in the sections, "calibration of the color camera" and "calibration of infrared camera", you can find that the camera parameters are different.

sir what does this line means in the link u've given: PointT& pt = cloud.points[v*w + u]; I was also doing similar thing, so got here, but didn't understand above line, else is good.